We think of the Border Collie as a diverse breed, at least in looks. But the Border Collie evolved from the working collies in the 18th and 19th centuries. These dogs were as diverse in looks as the Border Collie is today, and more so; but they were equally diverse in working style. Farmers, shepherds, and drovers selected and bred their dogs for the kinds of work for which they needed them, but also by personal preference, and no less according to what was available to them in their sometimes remote and isolated areas. From this diversity a number of types developed that today are considered separate breeds. Some, like the Border Collie, developed in Britain, others, like the Australian Shepherd, developed from the working collies that were brought to the United States or Australia and New Zealand. Some, like the English Shepherd, look today very similar to the Border Collie, and some, like the Bearded Collie, look quite different, or at least different enough so that you can distinguish them from the Border Collie by just looking at them. Where they differ most from the Border Collie (and sometimes from each other) are in their working styles. Still, they are all Collie breeds, and therefore cousins.

In 2004, Mark W. Neff, a veterinary geneticist at the School of Veterinary Medicine, University of California, Davis, and seven colleagues, wrote an article for inclusion in PNAS. In it they explained how their study determined that a mutation, found in the collie lineage, caused a sensitivity to certain drugs (including ivermectin). Based on breed histories, they concluded that all dogs that carry this mutation "are descendants of a dog that lived in Great Britain before the genetic isolation of breeds by registry (ca. 1873)." The mutation's history, they say "recounts the emergence of formally recognized breeds from an admixed population of working sheepdogs."

The authors used Linda Rorem's "Collie Family Tree" to select "collie-related breeds for testing" and say that it "was generally predictive of the observed distribution of the mutation, and the mutation was not found in any of the herding breeds whose origins traced back to continental Europe."

The authors had done their homework on the history of the collie breeds:

Dogs carrying the mutation share a common ancestor that experienced remarkable evolutionary success, having contributed genetically to at least nine distinct breeds of dog. We propose that this animal lived in Great Britain in the 1800s, before the emergence of formal breeds. Before 1870, there were no established registries for sheepdogs, only regional varieties of working dogs that had been adapted to terrain, climate, breed of sheep, and working style. Industrialization in the 19th century brought changes in trade and transportation that may have facilitated admixture among these varieties. Socioeconomic changes almost certainly altered the role of working dogs because they were no longer needed to drive sheep over long distances to market. Although a few specialized strains rose in prominence, perhaps aided by success at field trial events, many strains such as the Galway Collie, the Dalesman, the Manx Sheepdog, and the Welsh Gray gradually began to disappear. The neglect of regional varieties may have contributed directly to the advent of dog shows, which aimed to preserve and restore strains by emphasizing form rather than function. The first bench show to admit herding dogs took place in Birmingham in 1860, with one class open to all "sheepdogs, colleys, yard, or keeper's dogs." This show marked the beginning of an important transition in the history of sheepdogs, from regional variety to registered breed, and from anonymous working dog to pedigreed purebred.

From the point of view of the history of the Border Collie, this is an important study. Although some Border Collies do have a sensitivity to ivermectin, the mutation was not found in the Border Collie, so this study and it's findings, though not conclusive in this area, indicate that the Border Collie broke off from the rest of the population of old working collies of Great Britain and Ireland prior to the mutation. Collies, Australian Shepherds, Shetland Sheepdogs, English Shepherds, the McNab, and Old English Sheepdogs, all share a lineage that exhibits the mutation. The mutation was also not found in the Bearded Collie or Australian Cattle Dog.

There are twelve collie breeds (including the Border Collie) in the world today:

The Australian Shepherd, the Australian Kelpie, the Australian Cattle Dog (a.k.a. Blue Heeler or Queensland Heeler), the Collie, the Koolie (a.k.a. Coolie or German Coolie), the English Shepherd, the Old English Sheepdog, the McNab, the Shetland Sheepdog, the Bearded Collie, and the Welsh Sheep Dog.